The present disclosure relates to a vibrating device, and more particularly, to a piezoelectric vibrating device used in an electronic apparatus as a haptic feedback unit.
When pressure is applied to a piezoelectric material, a voltage occurs, which is a piezoelectric effect. When a voltage is applied thereto, an increase or decrease in a volume or length occurs due to a change in pressure in the piezoelectric material, which is an inverse piezoelectric effect. Piezoelectric vibrating devices use the inverse piezoelectric effect and generally applied to various electronic apparatuses such as cellular phones, portable multimedia players (PMP), and game consoles.
Piezoelectric vibrating devices used in cellular phones may be used as haptic feedback units responding to a touch of a user through vibrations. Haptic feedback designates a haptic sense capable of sensing by a finger tip or a stylus pen of a user when touching an object. Most desirable haptic feedback units are capable of replaying dynamic properties such as vibrations, touches, and an operation sound transferred to a finger when pushing a button as a response like touching a real button when a human touches a virtual object, for example, a button on a window screen. Accordingly, as an example of a piezoelectric vibrating device, Korean Patent Registration No. 10-0502782 (referred to as a cited invention 1) discloses a piezoelectric vibrating device attached with a plurality of piezoelectric element layers on one side or both sides of a vibrating plate. However, it is difficult to generate a full vibrating force necessary for an electronic apparatus by using a structure, in which piezoelectric elements are attached to the vibrating plate as disclosed in the cited invention 1. That is, amplitude of vibration is too small and the vibrating force is significantly smaller than a vibrating force generated by a coil type vibration motor using an electromagnetic theory or a solenoid type vibration apparatus currently used in cellular phones, thereby having no practicality.
To increase a vibrating force, Korean Patent Publication Application No. 2011-0045486 (hereinafter, referred to as a cited invention 2) discloses a piezoelectric vibrating device including a piezoelectric vibrating member generating vibrations, a weight vertically coupled with the piezoelectric vibrating member using a coupling member and amplifying a vibrating force, an a vibration supporting member fixing sides of the piezoelectric vibrating member. The piezoelectric vibrating device described above, for example, is provided in one area of a cellular phone and vibrates vertically to the cellular phone, thereby providing vibrations to the entire cellular phone.
However, the piezoelectric vibrating device of the cited invention 2 using the weight having great mass may be damaged at the piezoelectric vibrating member by impact. That is, while the weight is amplifying the vibrating force by vibrating within a preset range, when impact is given to the piezoelectric vibrating device due to a drop of the cellular phone, the weight moves more than the preset range. When the weight moves more than the preset range, impact is given to the piezoelectric vibrating member due to the mass of the weight, thereby damaging the piezoelectric vibrating member. As described above, when the piezoelectric vibrating member is damaged, since a haptic feedback does not occur, the piezoelectric vibrating device is driven to lose a function thereof.